Research interests

In the Walsh lab, we are exploring the ecological and biogeochemical implications of marine microbial diversity using molecular and genomic approaches. Currently, we are focused on several interconnected research themes:

Monitoring, modeling and predicting microbial community dynamics. A general goal in microbial ecology is to predict the response of microbial systems to external disturbances, for example, a warming climate. Currently, predictions are hindered by an incomplete understanding of how environmental and biotic factors influence microbial community structure and function. In the Walsh lab, we are using the coastal ocean as a model ecosystem in which to advance microbial ecology towards a predictive science. We are monitoring the composition of microbial assemblages in relation to a long-term, high resolution oceanographic time-series of abiotic and biotic conditions at a temperate coastal ocean observatory. Through repeated observation over multiple years, we are identifying re-occurring patterns in microbial genetic and functional diversity that will inform the construction of ecological models of coastal microbial systems.

Reconciling diversity: organic matter and microbial communities. Oxygen deficiency (hypoxia) occurs in marine regions where high productivity fuels intense microbial respiration. Although a natural phenomenon, evidence points to human-driven expansion of hypoxia in both the coastal and open ocean. Oxygen depletion in the open ocean is intensifying, potentially driven by current climate trends. Similarly, excess nutrient input from industrial and agricultural activities are leading to an increase in the number of coastal hypoxic regions. We are investigating the causes and consequences of marine hypoxia from a microbial ecology perspective by studying microbial communities associated with hypoxic bottom waters of the Gulf of St. Lawrence and several coastal marine basins.

Causes and consequences of marine hypoxia.
Oxygen deficiency (hypoxia) occurs in marine regions where high productivity fuels intense microbial respiration. Although a natural phenomenon, evidence points to human-driven expansion of hypoxia in both the coastal and open ocean. Oxygen depletion in the open ocean is intensifying, potentially driven by current climate trends. Similarly, excess nutrient input from industrial and agricultural activities are leading to an increase in the number of coastal hypoxic regions. We are investigating the causes and consequences of marine hypoxia from a microbial ecology perspective by studying microbial communities associated with hypoxic bottom waters of the Gulf of St. Lawrence and several coastal marine basins.

Selected publications

Walsh DA, Lafontaine J, Grossart HP. (2013) On the eco-evolutionary relationships of fresh and saltwater bacteria and the role of lateral gene transfer in their evolution. In Lateral Gene Transfer in Evolution, U. Gophna (Ed). 55-77.